How to choose the right crucible material for your alloy

The crucible is the one consumable in contact with every melt, so the material you choose sets the cleanliness of the metal, the life of the crucible and the cost per pour. This guide walks through how alloy, temperature and process point to the right choice.

Start with the alloy and the furnace

Begin with what you are melting and how. Air melting and vacuum induction melting place different demands on the refractory, and reactive alloys narrow the field further. A material that performs in an air melting foundry is not always suited to a vacuum furnace, and the reverse is also true.

Match the material to the temperature

Every material has a maximum service temperature. As a starting point across the Magna range:

• Alumina, up to 1800°C, the workhorse for a wide range of alloys in air and vacuum melting.
• Chrome alumina, up to 1800°C, for air melting where slag attack shortens crucible life. Not for vacuum work.
• Magnesia, up to 2000°C, for vacuum melting and very good resistance to basic slags.
• Super zirconia, up to 1900°C, magnesia stabilised for high end vacuum melting of aerospace alloys.
• Lime stabilised zirconia, up to 2200°C, for platinum group metal refining.

Consider slag chemistry and metal cleanliness

Slag chemistry decides how quickly a crucible wears. Basic slags favour magnesia; the glassy, siliceous slags of platinum melting favour lime stabilised zirconia. A dense, low porosity, non-wetting body keeps metal erosion to a minimum, which is what delivers clean metal with the fewest casting inclusions.

If you are unsure which material fits your alloy, furnace and melt size, our technical team will specify it with you. Send your details and we will recommend the right crucible.